Means for automatically adjusting arc furnace electrodes



Feb. 13, 1951 w. H. PAYNE 2,541,887

MEANS FOR AUTOMATICALLY ADJUSTING ARC FURNACE ELECTRODES Filed Sept. 1a,1943 INVENTOR. M l /arve :12

zi TTORNE Patented Feb. 13, 1951 MEANS FOR AUTOMATICALLY ADJUSTING ARCFURNACE ELECTRODES William Harvey Payne, La Grange, Ill.

Application September 16, 1943, Serial No. 502,649

1 Claim.

casioned by the melting down of scrap or other materials within thefurnace. Resulting effects require instant readjustment of the electrodeto the normal arcing position in order to maintain substantialuniformity in the power input to the electrode under conditions whichare well understood in the art, but which are set forth in full detailin my Patent No. 2,296,734, issued September 22, 1942, while the presentinvention also embodies certain of the principles defined in my PatentNo. 2,258,468, issued October 7, 1941. However, the present inventioninvolves numerous features of improvement over the patent last mentionedin that the whole structure is much simplified, and the counterbalancingpressure more direct y and advantageously applied, with resultingreductions in weight and cost of building and maintainance, andincreased reliability in operation.

In the means here involved, I impart to a column of liquid, preferablyoil, a constantly maintained pressure which exerts a lifting thrust onthe piston or equivalent means, which, when supplemented, acts directlyto raise or lower the mounting for the electrode. maintained pressure,being insufficient, unless augmented to overcome the weight of theelectrode and its mounting, serves however as a substantialcounterbalance therefor, so that a relatively slight addition theretowill cause the electrode-arm combination to be moved. Means aretherefore provided for augmenting this lifting effect in immediateresponse to variations in the electrical power input, which variationsare instantly reflected in the operation of a reversible motor drivenmetering pump, which in turn augments the normal counterbalancingpressure to the degree and for the period required to lift the electrodeto the extent necessary to reestablish normal arcing conditions, or, asoccasion requires, reverses the action to cause lowering of theelectrode by gravity where the augmented pressure is withdrawn. i Theemployment of an incompressible liquid column, under constantcounterbalancing pressure close to that required to efiect moving of theelectrode and its mountings," enables a prime mover, such as areversible motor of small power, to be employed for theoperation of ametering pump which is thus required only to augment the pressuresufliciently to overcome the differential,

This constantly trode.

thus reducing inertia to a minimum and speeding a prompt response tovariations in current conditions requiring a readjustment of the elec-'-Since almost instant reversals of the motor and pump are required atfrequent intervals to prevent hunting or lag in the sequence ofoperations and to keep the adjustments of the electrode in step withcurrent conditions, it is of major importance to reduce inertia to aminimum and to simplify the scheme of operations as much as possible. Itis also important to regulate the speed of the motor and pump in ratioto the extent to which the arcing gap deflects from its normal length sothat the speed of its return will progressively diminish as itapproaches its normal position, and it is likewise important to maintainuniformity in the action of the apparatus regardless of the burning awayof the electrode which depletion may result in variations of as much asthirty percent (30%) in the weight of the electrode and its mountings.These factors render it important to employ a metering pump which willat all times maintain a flow of oil in direct ratio to the speed of themotor which latter will accurately reflect the degree of maladjus'rmentof the electrode and vary its speed in ratio thereto. Thus a reversingprime mover unit may properly be called a meter motor because it metersand controls the electrode movement and speed through power applied toit in direct proportion to power input through its elec trode. Thepresent invention conforms fully to the above conditions andrequirements.

Further detai s will be apparent from the folr lowing description inconjunction with the accomnanying drawing, wherein:

Figure 1 is a diagram illustrating one form of ap aratus embodying thepresent invention; and

Figure 2 is a similar diagram illustrating an alternate form ofapparatus. r

Referring to Fig. 1, an electric furnace I0 is provided with anelectrode l I carried by an' arm l2 mounted upon a frame I3 verticallyadjust:- able between guide rollers Hi. The arm is acted upon by athrust rod l5 having at its lower end a piston l6 operable within acylinder IT. The thrust rod is preferably of a diameter closelyapproximating the internal diameter of the cylinvent the escape of anyappreciable quantity oi. oil or equivalent liquid. Oil is supplied tothe lower end only of the cylinder through a main duct I9 which is fedtoward the cylinder or drawn away therefrom, as occasion requires, bythe action of a metering pump 20, such, for instance, as a close fittinggear pump, which acts to meter the oil through in the required directionwithout appreciable leakage and at a computed rate, so that the actionof the pump, both as to the direction of flow imparted to the oil andthe amount delivered, will bear direct ratio to the speed imparted tothe gears or equivalent meter ing elements.

The pump in the present instance is driven by a prime mover in the formof a reversible electric motor 2|, the speed of which, in eitherdirection, will be controlled by the degree of readjustment required tobring the electrode to its normal arcing position. Such control of themotor is effected by means which are instantly responsive to variationsin the power input supplied to the electrode through electrical cables22 which, through suitable apparatus of known character, including acontrol circuit 23 and control appliances 24, will energize the motor 2|in proportion to are changes of the electrode. Such devices may beresponsive to changes in voltage or amperage, or various combinations ofthese two factors and further description thereof is deemed unnecessary.

The main duct l9 connects with a valve assembly which is showndiagrammatically, and which includes lateral ducts 25 and 26 and a crossheader 21, all of which are in communication with the main duct. Thelateral duct 23 and the adjacent end of the cross header are providedwith check valves 28 and 29, respectively, and the lateral duct 25 andadjacent end of the cross header are provided with relief and loadvalves 33 and 3|, respectively. The relief and load valves are normallyclosed by springs having a tension slightly in excess of the normaloperating pressure in the pipe 19. Relief and load valves 30 and 3|communicate with an oil return pipe 32 terminating in a down turnedelbow 33 which discharges near the bottom of a normally closed andsealed oil pressure tank 34. A supply pipe 35 leads from the base of thetank and communicates with the lateral pipe 25 and header 2'! throughcheck valves 28 and 23, respectively. A baffle plate 36 extends upwardlyfrom the base of the tank between the end of the return elbow 33 and thesupply pipe 35. Within the tank is a body of oil 31 under pressure of avolume of as (preferably air) which is trapped in the upper part of thetank and which constantly acts upon the column of oil exerting an upwardthrust against the piston and thus acting as a constant partialcounterbalance against the weight of the electrode and its mountings.

. For an apparatus of normal standard size a differential ofapproximately thirty (30) pounds between the down-thrust on the pistonoccasioned by the weight of the electrode and mountings and thetip-thrust against the underside of the piston is deemed satisfactory,it being understood that the weight should be suliicient only to ensurea prompt lowering of the electrode when augmented pressure is beingwithdrawn and the constant pressure only is effective, due account beingtaken of the fact that the aggregate load will vary within limits due tothe progressive depletion ofthe electrode.

: With the apparatus abovedescribed the meth- 0d involved in regulatingthe arcing gap is as follows: Under normal arcing conditions themountings for the electrode will stand stationary with a column of oilunder pressure trapped within the pipe l9, and with back-flow preventedby the check valve 28, the metering pump 20 and the load valve 3|, whichlatter should be loaded to a degree in excess of the assumed thirty (30)pounds preponderant weight on the top of the piston, as, for instance, aloading of thirty-five (35) pounds.

In the event the normal arcing gap is reduced and a rompt lifting of theelectrode is required. the control appliances will instantly respond andimpart an infeeding rotation to the motor and metering pump which willincrease the pressure in the liquid column causing additional oil toenter through check valve 29 to the intake side of the pump, so that theweight of the electrode and mountings will be overcome and the pistonwill rise until the approach and final restoration of normal arcingconditions slows down and final ly stops the operation of the motor.Conversely. if an abnormal increase in the length of the arcing gaprequires a lowering of the electrode, the motor and pump will bereversely operated and the pressure lowered by withdrawing a measuredquantity of oil through pipes l9 and 21 and through relief valve 3| tothe tank 34, and this action will continue until normal arcingconditions have been reestablished and the motor stopped, which willtrap the column of oil acting on the piston since the incompressible oilw act to positively block further movement. '1

The operations above described will occur in almost instantaneous accordwith variations in the power input and no lag will be occasioned by theemployment of such devices as electrically controlled valves which areobjectionable for the reason that the necessary valve overlap in othertypes of apparatus requires a preliminary readjustment before the valvebegins to act effectively with a corresponding lag in the readjustmentof the electrode itself, which is highly objectionable. Furthermore, anelectrically operated valve in the present art is not a metering devicesince the weight and friction of the electrode and support combinationconstitutes a substantial variable factor so that a controlled variationin the valve aperture does not accurately control the adjustment of theelectrode. The use of a pump which meters oil in direct relation topower input through its direct connection with a variably speededreversible motor or the like overcomes these objections, and bymaintaining the oil or equivalent liquid under constant pressure as apartial counterbalance and by the employment'o! gas (air) of negligibleinertia as the pressure medium, a small motor and pump of low inertiamay be employed which permits sudden reversals and prompt response toconditions in the power input.

The form of apparatus shown in Fig. 2 conforms in principle of operationto that previous:- ly described but is particularly designed for use incircumstances which render undesirable the employment of a closed systemunder air pres sures which may be safely maintained to afford thepartial counterbalancing effect which permits the use of a small motor.The use or a gaseous medium also requires the employment of a specialpressure surge tank 34 and a relatively large piston and cylinderbecause of the relatively low oil pressures which are limited by the airpres,- sure in the tank. In Fig. 2; the maintainance ot a constantcounterbalancing pressure is maintained, not by the provision of avolume of confined gas in a closed tank, but by the impulsion of aconstantly operating pressure pump unit which produces a like effect onthe column of oil. In the main, the apparatus is identical with thatfirst described, insofar as concerns the location and operation of themetering motor and pump, and check, relief and load valves, but in placeof the pipe 33 and tank 34, the following equipment is provided.

The return pipe 32 is carried beyond the load valve 3| in the form of anextension 38 terminating in a downturned elbow 39 opening near the baseof an open oil tank 46. A supply pipe 4| leads upwardly from the tankthrough the constantly operating pump 42 and makes connection with thepipe 38 through the relief valve 43. Oil under constant pressure fromthe pump 42 is admitted to supply the pipe 35 through the branch pipe 44provided with a gauge 45. A constantly operating motor 46 operates thepump to force oil into the pipe 44 and thus maintain the column of oilwhich acts on the piston under constant pressure approximating, but notequalling, the weight of the electrode and the mounting therefor. Sincethe motor 46 is constantly operating in one direction only it may be ofany required size and power to maintain the necessary constant uniformpressure on the oil, since problems attending the instant reversal ofthe motor 2| and the need for reducing inertia to a minimum have nobearing on the operation of the pressure motor 46.

In this form of apparatus the oil under the constant pressure of themotor 46 (in lieu of the gas confined within the tank 34) will, whensupplemented by the feeding action of the motor 2|, serve to overcomethe weight of the electrode and mountings and thus impart a liftingeffect in amount and during the time required to reestablish normalarcing or conversely lower the electrode by a reversal of theseoperations. As the piston is lowered the excess of oil will be forcedback through the pipes l9 and 21 and load valve 31, and through thepipes 38 and elbow 39 to the tank 4|]. This arrangement permits the useof a relatively small piston and cylinder and avoids the safety hazardwhich might attend the use of a large surge tank under the pressure of aconstantly confined gas.

In each of these constructions provision is made for the idlecirculation of oil through the system in the event the piston reachesthe limit of its up or down travel while the motor 2| continues tooperate. In such event on the upstroke of the piston, the continuedfeeding action of the pump would cause the relief valve 30 to open,thereby maintaining an oil flow through the pipe 32, elbow 33, pipe 21and check valve 29, back to the pump. On the downstroke of the piston,if the pump continued its reverse movement, the circulation would bemaintained through the pipe 21, load valve 3i, pipe 32 and elbow 33 (orthe pipe 38 and elbow 39 in Fig. 2), and thence from the oil tank 34 (or40) and back through the check valve 28 to the pump. Thus adequateprovision is made to permit the pump to operate in either directionwithout permitting the current flow to be blocked to an extent whichwould jam the pump and stall the motor.

By subjecting the column of oil or equivalent liquid to a constantpressure applied directly to the column itself, either by a trapped bodyof gas or by mechanical pumping effect, the employrnent of massivecounterweights of high inertia is avoided and at the same time only asmall differential in pressure is necessary to effect moving of theelectrode so that mechanical and electrical complications are reduced toa minimum, and prompt and accurate adjustments of the electrode in closestep with variations in the arcing gap are insured.

It will, of course, be understood that in all cases where a gaseousmedium is referred to, the same will ordinarily be air under pressureand that where oil is mentioned water or any liquid equivalent may beemployed which serves to maintain a substantially incompressible columnfor imparting movements to a piston or equivalent mechanism forimparting the required movements to the structure which carries theelectrodes. It will also be understood that the two examples ofmechanism here illustrated and described serve merely to exemplify theprinciples involved in the present electrode adjusting means, and thatthe same may find embodiment in structures involving numerous variationsin the location and details of the operating parts.

I claim:

An electric arc furnace comprising a vertically movable mounting, anelectrode carried by the mounting and provided with means for supplyingit with electric power input, a liquid column and telescopic confiningmeans therefor positioned to support the mounting, a source of liquid, aconduit between the source and the liquid, a reversible rotary meteringpump connected to the conduit and adapted when driven in one directionto supply liquid from the source to the column in order to augment thelatter and effect raising of the mounting and electrode and when drivenin the opposite direction to remove liquid from the column and therebyeffect lowering of said electrode, means for driving the pump in eitherdirection, controlled automatically in response to variations in saidelectric power input, and means for maintaining the liquid in theportion of the conduit between the source and the metering pump undersubstantially constant pressure of said magnitude as substantially tocounterbalance the weight of the mounting and electrode, said lastmentioned means consisting of a power driven pump in said portion of theconduit and an open-ended branch conduit leading from the conduit at apoint between the last mentioned pump and the metering pump and having apressure responsive relief valve therein.

WILLIAM HARVEY PAYNE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name a Date 264,346 Sedlaczek et a1. Sept.12, 1882 294,455 Earle et al. Mar. 4, 1884 1,646,048 Wirz Oct. 18, 19271,766,648 Keller June 24, 1930 1,909,659 Clapp May 16, 1933

